R30 Set-up

[Martin Mejia]

Hi guys,

I need a base setup for two R30 karts - one set up as a JR80 with front brakes and one as a JICA. Driver is really small, 4'10 about 85 lbs. What kind of axle should I start with (40mm, what type) and how wide in the front and rear should we be? I realize that initially i should just throw him in and let him drive ( get used to the brakes, powerband etc) but I want to be sure that the kart has a good base setup thrown onto it.... Any help would be greatly appreciated. Thx.

Martin

[Chris Lobaugh]

For the 80cc application I would say either a short M or a long F3 at 54-54 1/2" with standard hubs. Front should be 4 lines out with the spindles down and 0 pills. Depending on the track and the driver you may add a bit of caster or raise the spindles up.
For Jica I would day a long F3 down to a short F2.5 depending on the track and the conditions. If you are using old (three race weekend) tires than you will probably be better off on the harder end. I almost always ran with the spindles down and at least 1.5 degree of caster with an R30/100cc application. Start with the spindles down and caster in. If the driver complains that the kart has too much front grip than pulll the front bar out and try that. If you are using truck hubs use 2 thick spacers wide in the front, if bearing mount wheels use 3 1/2 thick spacers in the front. For rear track width: measure fron the cassette to the outside edge of the wheel hub 23.6cm will be right out at 55" with 7.1"tires but only 53 1/2" with 6.0 tires. I've never run wider that 23.6cm so that will be something to experiment. For the new driver, though, I would start at 531/2" and then move them out as the speed comes up. Hope this helps.

[Martin Mejia]

In regards to the axles mentioned, are those 50mm or 40mm axles? (R30 is 40mm stock).

Also, I want to try and understand the reasoning tor running the different front caster setups - 0 for the Jr 80 and 1.5 for the JICA. What does that accomplish and why the difference? Just trying to understand everything so I know what's going on.... thx again.

Martin

[Chris Lobaugh]

With an R30 in Jr. applications running on YHC tires I would stick with the 40mm stuff. The differnce in front end settings is due to the difference in power, gearbox, weght, and front brakes. More caster will help the kart jack and twist. With lower horsepower applications and especially with small drivers you need more caster to make the kart "work". By "work" I mean lift the inside rear tire off the ground. This is what we are trying to accomplish. I hope this helps.

[Martin Mejia]

My computer crashed and never got to your response, thanks by the way. So far this is what I understand and correct me if I got it wrong:

[Martin Mejia]

Just hit he wrong key there. Anyway here is what I understand so far:

1. Caster is more critical for low hp karts and it really needs to get up, while for more powerful karts-shifter- you can get away w/ less caster as it can power thru the turns better;

2. Spindle height affects the caster requirements of the kart. Higher spindle needs more caster & lower spindle requires less caster. Pls explain why? and also how does it relate to front track width(spindle height)

3. Last thing, Jr 80 on 40 mm axle? Is 50 mm too stiff or what is the reasoning why you think 40 mm would work better in this application?

Thanks....

[Martin Mejia]

Chris,

I just re-read my post above(item #2), and I think I said things backwards:
>
> " 2. Spindle height affects the caster requirements of the kart. Higher spindle needs more caster &
> lower spindle requires less caster. Pls explain why? and also how does it relate to front track
> width(spindle height)"
>
From what you said, conclusion should be higher spindle requires less caster and vice versa.

My other questions - why?, spindle height vis-a-vis front track?, 40 mm ? - I'm still clue less. Thanks in advance for the helpfor the help.